The present invention generally relates to powering electrical devices using data cabling. More specifically, the present invention relates to extracting electrical power from data cabling.
Power Over Ethernet (POE) is a means for powering network connected devices known as Powered Devices (PDs) that are remotely located. The PDs are powered through a low voltage data cable, without the need for a line from an AC power source to each PD. In most cases, a standard eight wire Ethernet cable transports the power over two or all four wire pairs. In order to avoid damaging connected devices, Power Sourcing Equipment (PSE) applies a limited detection voltage to the PD. If the PD is designed to be powered by POE, the PD will present a signature load to the PSE. Upon detecting the signature load, the PSE will increase power sourcing until power is available to match the power class of the PD. If there is not a signature load, the PSE will not send power to the PD.
Traditionally, network connected devices such as PCs, laptops, IP phones, wireless LAN access points, net cameras, etc. have required both a data connection and an AC line power connection. Given the increasing number of network connected devices, the AC line power, generally installed by an electrician to code standards, is an expensive component of the overall system deployment. POE eliminates the need for additional AC power outlets and labor costs associated with installation, by sourcing the power in the network core, and distributing it over the data cable. Another advantage of POE is that it supports a point to multi-point power distribution architecture, carried over the existing data network. This lets network managers use a single Uninterrupted Power Source (UPS) at the network core to back-up power to multiple devices connected to the Local Area Network (LAN).
The Institute for Electrical and Electronic Engineers (IEEE) has standards (IEEE 802.3af and 802.3 at) that define PSE and PD design, such that products from different manufacturers are interoperable. Herein, the term POE shall encompass both standards compliant (802.3af and 802.3 at) and non-standard methods of using a POE. IEEE802.3af POE standards prescribe delivery of nominally 48 Vdc over two unshielded twisted pairs of standard data cabling. New, higher power IEEE 802.3 at standards for the POE and POE Plus specify that power is carried on all 4 wire pairs. The POE works over existing data cable including category 3, 4, 5e, or 6 data cables; horizontal and patch cables, patch panels, outlets and connecting hardware, without modification. Specifications for standard POE specify that a minimum 320 milliamps at 48 V (15.4 W) is sourced by the PSE. Due to the resistive loss on a 95m Ethernet data cable, the total minimum amount of continuous power that can be delivered to each node is specified as 12.95 W. Usually, the POE system is tolerant of a 2.45 W of power lost in the data cable. IEEE 802.3 at and POE Plus define a method to supply about 30 W to the PD using about 720 mA of current on each conductor of the data cabling.
The PSE contains a sensing mechanism to prevent sending power to non-standard compliant equipment. Only PDs that present an authentic POE signature to the PSE will receive power, preventing damage to non-standard compliant equipment. There are two types of PSE. The first is an End-Span switch and the second is known as mid-span panels. An end-span switch refers to an Ethernet switch with built-in POE capability. The end-span switches deliver data and power over the same two wiring data pairs of pairs 1/2 and 3/6. Mid-span panels resemble patch panels. The mid-span panels are placed between the PD and the Ethernet switches which do not have POE capability. The Mid-span panel receives the data alone in an RJ-45 input connector and delivers the data plus power in an RJ-45 output connector. The mid-span panel uses the two unused wiring pairs of pairs 4/5 and 7/8 to carry the power, while data runs on the data pair. Both End-span and Mid-span equipment deliver power and data directly to the PD and the PD can be conveniently placed at the point of use. For IP Phones, desktop PCs, and laptop PCs, the point of use is desktops throughput the workplace. For wireless access points and IP cameras, the point of use is ceilings and walls throughout the facility. For network connected industrial automation devices, the point of use may be throughput the factory or warehouse.
Current POE systems do not have provisions by POE to power other accessories, such as amplifiers, detectors, sensors, transducers, electronics, cameras, switches or wireless devices, which may be beneficially co-located with the PD that is powered by the POE system. Nor is there a convenient method of connecting these accessory devices, which may have a data output, to the network core. An example would be use of remote accessories such as a heat sensor, air quality sensor, sound sensor, or wireless transceiver co-located in the ceiling with a PD such as a wireless access point. Although the wireless access point PD is network connected and powered via POE, the co-located sensor will still require an AC line power connection and an additional data connection to the network core. Another example is Ethernet network used in industrial automation. POE enables automation equipment PDs to be powered by the data cable, but accessories co-located with the automation equipment PD, such as pressure and temperature transducers, are not connected to the POE power, nor connected to the POE to transmit their data on the network.
Another drawback to current POE systems is that POE and PDs may be sensitive to damaging voltage surges on the data cable. These power surges may be caused by lightning, short circuits, device failure, or inappropriately applied voltage. Network wide power surges could damage many PDs connected to the network. Most network connected equipment is inadequately protected from common mode and differential mode surges on the data cables. Existing Ethernet surge protection products preclude the use of POE, as they have the effect of shorting the DC power provided by the POE.
It is an object of the present invention to provide a device and method of use to extract power traveling to a PD to power remote accessories.